Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Current assets:
Cash and cash equivalents	$ 556	$ 81
Accounts receivable, less allowance for expected credit losses	476	427
Production fuel, at weighted average cost	46	54
Gas stored underground, at weighted average cost	49	55
Materials and supplies, at weighted average cost	193	186
Regulatory assets	155	210
Other	222	171
Total current assets	1,697	1,184
Property, plant and equipment, net	20,344	18,701
Investments:
ATC Holdings	463	415
Other	231	224
Total investments	694	639
Other assets:
Regulatory assets	2,119	2,064
Deferred charges and other	137	126
Total other assets	2,256	2,190
Total assets	24,991	22,714
Current liabilities:
Current maturities of long-term debt	1,074	1,171
Commercial paper	88	558
Accounts payable	498	532
Accrued interest	124	112
Regulatory liabilities	88	69
Other	251	273
Total current liabilities	2,123	2,715
Long-term debt, net (excluding current portion)	10,954	8,677
Other liabilities:
Deferred tax liabilities	2,310	2,188
Regulatory liabilities	1,113	959
Pension and other benefit obligations	173	224
Other	984	947
Total other liabilities	4,580	4,318
Commitments and contingencies (Note 16)
Common Stock, Shares, Issued	257,137,261	256,690,222
Common equity:
Common stock	$ 3	$ 3
Additional paid-in capital	3,101	3,060
Retained earnings	4,243	3,954
Accumulated other comprehensive income	1	1
Shares in deferred compensation trust - 367,338 and 372,116 shares at a weighted average cost of $39.05 and $36.56 per share	(14)	(14)
Total common equity	7,334	7,004
Total liabilities and equity	24,991	22,714
IPL [Member]
Current assets:
Cash and cash equivalents	7	29
Accounts receivable, less allowance for expected credit losses	185	192
Production fuel, at weighted average cost	18	30
Gas stored underground, at weighted average cost	24	25
Materials and supplies, at weighted average cost	111	113
Regulatory assets	59	77
Other	58	43
Total current assets	462	509
Property, plant and equipment, net	10,436	9,336
Other assets:
Regulatory assets	1,557	1,509
Deferred charges and other	40	53
Total other assets	1,597	1,562
Total assets	12,495	11,407
Current liabilities:
Current maturities of long-term debt	0	300
Commercial paper	88	50
Accounts payable	232	263
Accounts payable to associated companies	45	47
Accrued taxes	53	77
Accrued interest	47	48
Regulatory liabilities	41	54
Other	80	89
Total current liabilities	586	928
Long-term debt, net (excluding current portion)	4,680	3,790
Other liabilities:
Deferred tax liabilities	1,278	1,179
Regulatory liabilities	545	492
Pension and other benefit obligations	30	46
Other	532	511
Total other liabilities	2,385	2,228
Commitments and contingencies (Note 16)
Common Stock, Shares, Issued	13,370,788	13,370,788
Common equity:
Common stock	$ 33	$ 33
Additional paid-in capital	3,497	3,212
Retained earnings	1,314	1,216
Total common equity	4,844	4,461
Total liabilities and equity	12,495	11,407
WPL [Member]
Current assets:
Cash and cash equivalents	37	51
Accounts receivable, less allowance for expected credit losses	273	220
Production fuel, at weighted average cost	28	24
Gas stored underground, at weighted average cost	25	30
Materials and supplies, at weighted average cost	81	69
Regulatory assets	96	133
Prepaid gross receipts tax	52	51
Other	59	57
Total current assets	651	635
Property, plant and equipment, net	9,363	8,861
Other assets:
Regulatory assets	562	555
Deferred charges and other	79	55
Total other assets	641	610
Total assets	10,655	10,106
Current liabilities:
Current maturities of long-term debt	0	0
Commercial paper	0	183
Accounts payable	197	209
Accrued interest	46	44
Regulatory liabilities	47	15
Other	105	94
Total current liabilities	395	545
Long-term debt, net (excluding current portion)	3,669	3,370
Other liabilities:
Deferred tax liabilities	861	865
Regulatory liabilities	568	467
Pension and other benefit obligations	75	102
Other	712	656
Total other liabilities	2,216	2,090
Commitments and contingencies (Note 16)
Common Stock, Shares, Issued	13,236,601	13,236,601
Common equity:
Common stock	$ 66	$ 66
Additional paid-in capital	2,613	2,533
Retained earnings	1,696	1,502
Total common equity	4,375	4,101
Total liabilities and equity	$ 10,655	$ 10,106